Much of the early mortality seen in multiple sclerosis patients is related to their smoking habits, study shows.

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LYON, France — SATURDAY, Oct. 13, 2012
(MedPage Today) — Much of the early mortality seen in multiple
sclerosis patients is related to their smoking habits, a researcher said
here.

In a prospectively followed cohort of nearly 900 MS patients, 68
percent of those who died in a 40-year period were current or former smokers,
compared with 50 percent of surviving patients, according to Ali Manouchehrinia
of the University of Nottingham in England.

After adjusting for sex, age of MS onset, initial diagnosis (relapsing
versus progressive MS), and use of disease-modifying drugs, the mortality rate
for smokers was higher than non-smokers, he told attendees at the European
Committee for Treatment and Research in Multiple Sclerosis annual
meeting.

The mortality rate in ever-smokers was 5.48 per 1,000 person-years,
compared with 2.30 per 1,000 person-years among the lifetime nonsmokers in the
cohort.

Of the 66 patients in the cohort who died, 45 (68 percent) were
smokers; 49 percent of the entire cohort were smokers.

Manouchehrinia noted that deaths among never-smokers in the cohort
still tended to be premature relative to the general population. But the
difference was less than half that seen among patients with a smoking
history.

He also indicated that age of onset of significant disability was
slightly younger in the ever- versus never-smokers, but the net result was that
the never-smokers lived longer with disability, on average.

Overall life expectancy among MS patients is about 5 years less than
in other people, for reasons that are unclear. Smoking, however, is a strong
epidemiological risk factor for development of MS, which also means that
smokers are overrepresented in MS patients relative to the general
population.

Because smoking is itself associated with a substantial reduction in
life expectancy, Manouchehrinia said, he and his colleagues sought to determine
how much it may contribute to early mortality in MS patients.

They examined data on 895 MS patients registered at Nottingham
University Hospital who had been followed for up to 40 years after diagnosis.
Smoking status was recorded in the data. A total of 66 patients in this cohort
had died as of December 2011.

Average age at death was 65, whereas the mean age of survivors as of
December 2011 was 52. Decedents were also largely male (58 percent), whereas 72
percent of survivors were women.

The distribution of diagnoses also differed significantly between
decedents and survivors. Half the survivors had relapsing forms of the disease,
compared with only 12 percent of patients who had died. Two-thirds of the
decedents had secondary progressive disease at last follow-up, compared with 38
percent of the survivors.

The differences largely reflected the older age of decedents, although
Manouchehrinia noted that other research has suggested that disease progression
is faster in smokers.

Another difference between decedents and survivors was that 44 percent
of the latter had received at least a year of disease-modifying therapy,
compared with only 13 percent of those who died.

Such disparities necessitated a multivariate analysis to assess the
role of smoking in mortality. After adjusting for these factors, it remained
the case that smoking approximately doubled the risk of death in the cohort,
Manouchehrinia said.

A Kaplan-Meier curve showed that, with disease duration of 45 years,
the survival rate among ever-smokers was 50 percent compared with about 75
percent in lifetime nonsmokers.

The researchers also calculated that, compared with life expectancy in
the general population, a total of 1,779 years of life were lost prematurely in
the cohort — 62 percent of which were in ever-smokers.

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